How to: High poly to low poly normal map + high poly texture + normal map of texture detail
You said you know how to bake a normal map from hi-poly to low-poly. It's the same for color texture.
If you use blender internal, bake textures instead of normals in the menu.
In cycles, you can choose 1 of the 3 diffuse maps (color, direct, indirect). The diffuse color should be what you need but if you want to combine the 3, you have to add direct to indirect and multiply the result with color.

About normal map : painting a normal map is a bad idea. Some softwares allow you to do it but if you want to paint details, use a bump map (B&amp;W). I'm not sure about that but I think the normal baking adds the bump map inside the resulting normal map (blender internal). Else you'd better paint it on the low-poly mesh.